ci: Remove the autotools install from the Linux verification job

All necessary autotools packages are now preinstalled in the GitHub
Actions Ubuntu runner images.

This is a cherry-pick of commit 964b4135949703b705fc760fc3fb546b86e5ab47
from branch 'libpng18'.

.github/workflows/verify-linux.yml

diff --git a/.github/workflows/verify-linux.yml b/.github/workflows/verify-linux.yml
index 8f839a5..e32bfc8 100644
--- a/.github/workflows/verify-linux.yml
+++ b/.github/workflows/verify-linux.yml
@@ -22,16 +22,9 @@
     timeout-minutes: 10
     steps:
       - name: Install dependencies
-        env:
-          BASE_REF: ${{ github.base_ref }}
-          REF_NAME: ${{ github.ref }}
         run: |
           sudo apt-get update -qq
           sudo apt-get install -y --no-install-recommends build-essential zlib1g-dev
-          if [[ "$REF_NAME" != refs/*/libpng16 && "$BASE_REF" != libpng16 ]]
-          then
-            sudo apt-get install -y --no-install-recommends autoconf automake libtool m4
-          fi
       - name: Check out the code
         uses: actions/checkout@v4
       - name: Run the configure verification script